1. Field of the Invention
This invention relates to an on-vehicle brake lamp which lights up or light out in interlocked relation with brake operation of a vehicle.
2. Prior Art
Conventionally, incandescent bulbs have been used as on-vehicle stop lamps of vehicles that are lighted up or lighted out by means of a switch drivingly connected to a brake pedal. Recently in U.S.A., a second stop lamp called a high mount stop lamp, mounted near a rear window, has been obligated by law. Also in Japan, many vehicles have been equipped with such stop lamps these days since this type of stop lamp exhibits good visibility to other drivers following behind, reducing rate of accidents. The lamps used for the high mount stop lamp, however, are of the same type as that of stop lamps at the rear of the vehicles, i.e., conventional incandescent light bulbs. An incandescent lamp suffers from a drawback that it takes a long time, for example many tens msec, before it emanates a light after it is switched on. Recently, rare gas discharge lamp such as a neon gas lamp began to be used as an on-vehicle high mount stop lamp and the like for its good light emitting efficiency and low power dissipation. This was reported by a news paper NIKKEI SANGYO SHIMBUN on Sept. 30, 1988 in Japan. The amount of light emitted by the neon lamp increases with increasing discharge current. Conventionally, a neon discharge lamp has been of a cold cathode type. The cold cathode discharge lamp has a limited maximum amount of light obtained; therefore a hot cathode type neon discharge lamp such as that disclosed in U.S. Pat. No. 4461981 has been preferred. Heating the hot cathodes at all times allows the lamp to light up in a short time but the lamp sometimes needs be lighted up rapidly even when the hot cathodes are not heated, for example, when a vehicle key is not inserted into the key hole of the vehicle. Therefore the time required for the hot cathode lamp to light up can be a problem. The present invention was made to overcome the aforementioned drawbacks.